Blocked Plate Heat Exchanger (Sludge) | No Hot Water | How To Unblock | Viessmann Boiler

Breakdown & Wiring Book: https://book.advancedboilertraining.c... In this video I show how to unblock a plate heat exchanger on a Viessman combi boiler. A sign you will need to do this is when the hot water keeps going from hot to cold but the heating (radiators) work fine. Over time sludge builds up in the plate and causes the boiler to overheat as the water can not circulate properly due to it being blocked. Tools used in this video: Draper Screwdriver Roll/Set: https://amzn.to/3Xmh6Zz Bahco Adjustable Spanner: https://amzn.to/3lupI3c